Forced-circulation boiler system with separate boiler and furnace



Ap rll 21, 1970 w, SANDER 3,507,256

FORCED-CIRCULATION BOILER SYSTEM WITH SEPARATE BOILER AND FURNACE Filed Aug. 26, 1968 "F: w 7 7 1 A i f 19- i '5 1 g I I 1 Ii 1 i i T.J I I i l.

F I61 I I l J H 1 5 i753 51224? I i l I i United States Patent Othce 3,507,256 FORCED-CIRCULATION BOILER SYSTEM WITH SEPARATE BOILER AND FURNACE Wolfgang Sander, Heidelberg, Germany, assignor to Konus-Kessel Gesellschaft fur Warmetechnik m.b.H. & Co. K.G., Hockenheim, Germany Filed Aug. 26, 1968, Ser. No. 755,310 Int. Cl. F22b 33/00; F22d 7/12 US. Cl. 122-20 9 Claims ABSTRACT OF THE DISCLOSURE DRAWING FIG. 1 diagrammatically illustrates an installation according to one embodiment of the invention;

FIG. 2 illustrates a safety flap detail on enlarged scale; and

FIG. 3 is a schematic diagram of a switching arrangement for the safety flap.

Detailed description This invention relates to forced-circulation boiler systems for the purpose of heating heat-transfer liquids such as oil, which must be protected against overheating, which boiler systems are of the type which includes an electrical circulating pump, a boiler housing, a tubular coil incorporated into said housing and containing the liquid, and a smoke stack for exhausting smoke and gaseous combustion products from the forced-circulation boiler system.

In known systems of this kind, the heat-transfer liquid is circulated through a sealed tubular coil system by an electrical pump. The heating of the heat-transfer liquid is effected by means of burners attached to the boiler frame, which burn gaseous or liquid fuels. A smoke stack serves for eliminating the gaseous combustion products from the boiler.

An object of the present invention is to provide forcedcirculation boiler systems as heretofore described, in such a manner that solid fuels may also be utilized for heating the heat-transfer liquid.

The burning of solid fuels in a boiler system of the kind described involves difliculties, since the combustion of solid fuels cannot be regulated or controlled as precisely as is possible with gaseous or liquid fuels. If, for example, the maximum temperature permissible for the boiler has been attained and if solid fuels were being burned, it would not suffice to shut off the fuel supply because the glowing, partially consumed fuel pieces present in the boiler would continue to act, causing overheating of the tubular coils and of the heat-transfer liquid therein contained.

The same problem of overheating the tubular coils and their contents can arise if the voltage supply to the electrical circulating pump should fail. When liquid or gaseous fuels are burned, failure of the electric pump system usually coincides with shut-down of the burners because, in case of failure of the circulating pump, the burner for liquid, or gaseous fuels can be made to shut down auto- 3,507,256 Patented Apr. 21, 1970 matically. Thus, even with a failure of the electrical circulating pump, overheating need not normally be feared in liquid-fuel or gaseous-fuel boiler systems.

Finally, the utilization of solid fuels in boilers of the kind described would also lead to serious difliculties concerning slag disposal.

The invention makes possible the utilization of solid fuels for firing boilers of the kind described by providing a separate furnace chamber connected to the forced-circulation boiler by a flue, as well as a safety device automatically shutting off the supply of smoke gas through this flue to the boiler in case of pump failure. This arrangement assures against any overheating of the heattransfer liquid. At the same time, all slag disposal problems, which would arise with the known type of forcedcirculation boilers, are eliminated.

According to an advantageous embodiment, a by-pass pipe provided with shut-off means leads from the flue to the smoke stack including means for automatically causing the shut-off means to open the by-pass pipe if the circulating pump fails. As soon as this by-pass pipe is opened, the smoke gases from the furnace flow directly through the by-pass pipe into the smoke stack of the boiler, since this by-pass pipe offers them much less resistance than the boiler. A particular advantage of this arrangement consists in the fact that combustion of the solid fuel may continue even when the safety device has been actuated.

Although the shut-off means of the by-pass pipe can be controlled, for example, by a sensor monitoring the circulating pressure inside the liquid system, preference is given, for the sake of simplicity, to an arrangement wherein the shut-off means will assume its position freeing the by-pass tube when the power supply to the electrical circulating pump fails. As soon as this emergency arises, the shut-off means moves to its position freeing the by-pass tube and the smoke gases flow directly from the furnace chamber to the smoke stack.

Actuation of this shut-01f means is preferably done electromagnetically. The design of this shut-off means may, for example, be such that it is maintained in its closed position by a compressed-air cylinder, the air pressure in the cylinder being maintained by a solenoid. If the voltage fails, the air can escape from the cylinder and the shut-off means thereupon moves to its open position by spring-pressure or by gravity. Advantageously, this arrangement is provided in such a manner that, upon return of the voltage, a second solenoid takes care of resupplying the cylinder with compressed air whereby the shut-off means is returned to its normally closed position. Various other embodiments of a solenoid-controlled shutoff means can also be considered.

The shut-off means in its simplest configuration is a pivoting flap. The smoke-gas conducting flue and the bypass pipe are advantageously connected to the boiler over a removable T pipe fitting.

This arrangement makes it possible, in case of operating trouble in the furnace chamber or in case of failure of same, to disconnect the boiler from the furnace chamber, and, in lieu of the T-piece, to assemble a burner, e.g. an oil burner to the boiler, so that heating of the heattransfer liquid in the boiler can still be assured. After disassembly of the T-piece the open ends of the bypass pipe and of the smoke-gas conducting flue are closed off appropriate blind flanges.

The burner preferably used for this purpose will be a burner capable of producing inside the furnace chamber the temperature necessary for igniting the solid fuel used in said furnace chamber. For this purpose, the arrange ment is made in such a manner that the furnace chamber is provided with an auxiliary burner for liquid or gaseous fuels and that its connection for this burner and the connection of the boiler for the T-piece are identical.

In the following, a forced-circulation boiler according to the invention is described on the basis of the attached drawing.

The forced-circulation 'boil l'in FIG. 1 is preceded by a vertical furnacec hamber 2 to which solid fuel, for example, scrap wood is supplied by means of a screw conveyor 14. The combustion air is supplied by a blower 27.

The smoke gases generated in the furnace chamber 2 are supplied to the boiler 1, inside of which the tubular coil 12 contains the circulating heat-transfer liquid, via a flue 3 and are exhausted from the boiler through a funnel 11 via a heat exchanger 9 and a blower 10 to a smoke stack 4. The pump 13 serves for circulating the heattransfer liquid.

A burner 8 is provided on the furnace chamber 2, which serves for initial heating up of the furnace chamber until the ignition temperature for the solid fuel is attained. The flue 3 is connected to the smoke stack 4 by a by-pass tube 5. A shut-01f flap 6 shown schematically in FIG. 1 closes off the by-pass tube. This flap is solenoidioperated. In case of failure or interruption of the power supply, the flap 6 automatically opens the by-pass connection between the flue 3 and the smoke stack 4.

Before entering the boiler, the heat-transfer liquid is pre-heated in the heat exchanger 9 by the smoke gases exhausted from the boiler. The exhaust blower 10 assures a constant draft. The smoke-gas supply flue 3 and the bypass tube 5 are connected with each other by means of a removable T-type pipe fitting 7. The shut-off flap 6 is preferably located in this T-piece, facilitating its inspection, removal and replacement. I

If the burner 8 is to be assembled directly on the boiler, the open ends of the by-pass tube 5 and the supply flue 3, after removal of the T-pipe fitting, are closed off by blind flanges.

As shown in FIG. 2, the safety flap 6 is supported by a horizontal shaft on hearing recesses in the T-piece 7. On the side visible in FIG. 2, the shaft 15 is bent to the left by 90 degrees and carries a weight 17 at its end, which will tend to tilt the flap -6 to a horizontal position. The bent-away part 18 of the shaft 15 carries an anchor plate 19, which is attracted to the soft-iron core 20 of the sole noid 21 as long as the coil 22 (FIG. 3) of the solenoid carries current. If the current ceases, the solenoid releases the anchor plate, and the safety flap 6 tilts to its horizontal position due to the gravity acting on weight 17 and, in this position, permitting the smoke gases to escape through the by-pass tube 5.

The solenoid 21 is connected in such a manner that it is de-energized, if the circuit of the circulating-pump 13 is interrupted, by means of a solenoid 23 which is in series with the pump motor and which maintains closed a switch 24 in the circuit of solenoid 21 and which solenoid 23 maintains closed as long as it remains energized.

Further switch 25 in the circuit of the solenoid 21 is controlled by a solenoid 26. This solenoid will open switch 25 if and when a temperature detector arranged in the boiler 1 senses a temperature rise beyond a certain preset maximum value, whereupon it will actuate the solenoid 26.

What is claimed is:

1. A forced-circulation boiler system for the heating of a heat-transfer liquid which must be protected against overheating, comprising an electrical circulating pump for the forced circulation of the heat-transfer liquid, a boiler housing, a tubular coil system in said housing and coupled to said pump, a smoke stack for exhausting the smoke gases from the boiler housing, a smoke-gas conduction flue, a furnace chamber separate from but connected to the boiler housing by said smoke-gas conducting flue, and a safety device means coupled to said pump to suppress the supply of smoke gas to the boiler housing in case of pump failure.

2. A boiler system according to claim 1 comprising a by-pass tube leading from said fiue to said smoke stack and a shut-0E device means normally closing said by-pass tube but eifective to open the by-pass tubes in case of pump failure.

3. A system according to claim 2, wherein the shut-off device means assumes a. position for opening the by-pass tube in case of failure of power supply to the electrical circulating pump.

4. A system according to claim 3 comprising means by which the shut-off device means is actuated electromagnetically.

5. A system according to claim 2 wherein the shut-off device means is a tiltable flap operatively associated with said by-pass, tube.

6. A system according to claim 2 comprising and wherein the smoke-gas conducting flue and the by-pass tube are connected to the boiler housing by a T-pipe fitting.

7. A system according to claim 6 wherein the safety device means is located inside the T-pipe fitting.

8. A system according to claim 6 comprising, in operative association with the furnace chamber, an auxiliary fuel burner, and means connecting the same on the furnace chamber.

9. A system as claimed in claim 8 wherein the latter said means is a T-pipe fitting.

References Cited UNITED STATES PATENTS 2,074,989 3/ 1937 Orban l2220 2,252,046 8/1941 Steele 122-20 XR KENNETH W. SPROG'UE, Primary Examiner US. Cl. X.R. 

